Apparatus for generating multiple signals with independently controllable phase differences and frequency



Oct. 24, 1961 B. D. I EVENSON 3,005,960

APPARATUS FoR GENERATING MULTIPLE SIGNALS WITH INDEPENDENTLY CONTROLLABLE PHASE DIFFERENCES AND FREQUENCY Filed Jan. 24, 1958 5)/ JJ g Aang/v7,-

3 005 960 APPARATUS FR GEEATING MULTIPLE SIG- NALS WITH INDEPENDENTLY CNTRLLA- BLE PHASE DBFFERENCES AND FREQUENCY Berl D. Levenson, Los Angeles, fraihrnssignorfte Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Filed Jan. 24, 1958, Ser. No. 711,102 7 Claims. (Cl. S31-25%)V The present invention relates to signal generating apparatus and more particularly to an apparatus for generating a plurality of signals of yan independently controllable frequency, successive ones of the signals having uniform phase differences which may be independently controlled electronically without -alfecting the frequency.

r[he apparatus of the present invention is particularly adapted for use in `conjunction with an electronic scanning -radar system wherein the phase difference between successive signals determines the direction of a pencil receiving beam. An electronic scanning radar system of this type is described in a co-pending application for patent, Serial No. 707,068, entitled, Electronic Scanning Radar System, led by Berl D. Levenson and William R. Welty on lanuary 3, 1958 and assigned to the same assignee as in the present case. In the operation of a radar system of the aforementioned type, it is often necessary to change the direction of the pencil receiving or transmitting beam in an extremely short interval of time. Because of this, it is highly desirable to use an entirely electronically controlled apparatus, to effect a change in direction of the pencil beam. A mechanical apparatus, on the other hand, possesses inherent inertia which places limitations on its use. Also, when the apparatus of the present `invention is used in conjunction with the above type of electronicscanningradarrsystem,ttthetirequency..

of plurality of signals generated by the present apparatus must be mixed with a rst intermediate frequency of the radar system and filtered to result in a second intermediate frequency in the systemfr Henceitaisnviflent l that it must be necessary to control the frequency of the plurality of signals generated by the instant apparatus independently from any changes in the phase differences between the signals. Further, the apparatus of the present invention provides more accurate phase differences than is generally possible by using mechanical expedients.

In accordance with the present invention, a delay line which may comprise a sinuous feed is provided with a plurality of uniformly spaced points therealong Where electromagnetic energy may be coupled therefrom.V A corporate feed is also provided which has a corresponding number of output junctions. In operation, the delay line is adapted to receive a first signal from the variable frequency microwave source. Variations in this frequency will, of course, produce changes in the phase dierences between the signals appearing at the uniformly spaced points along the delay line. this source is also mixed with a second signal provided by a second source in a manner to subtract the two frequencies, the resultant signal being filtered and applied to the corporate Vfeed apparatus. Each of the signals appearing at the successive points along the delay line are applied together with an output signal from the corporate feed to a mixer which functions in a manner to subtract the frequency of the two signals. The output signals from the successive mixers are then filtered and result in a plurality of signals, successive Ones of which have a phase difference controlled by the frequency of the first signal. The frequency of each of the plurality of output signals is, however, determined by the frequency of the second signal.

The signal rfrom Y The above-mentioned and other features and objects of this invention and the manner of attaining them be-v come more apparent by reference to the following description taken in conjunction with the accompanying ,lrawing where@ the ligure lillustrates aschem-atic blockv diagram of the apparatus of the present invention.

Referring now to the drawing, the apparatus of the present invention comprises a delay line d0 which has la plurality yof m output junctions spaced at uniformly spaced 10 points therealong. The delay line l!) may constitute, for

example, a length of coaxial transmission line or waveguide. Further, the transmission line or waveguide may be arranged in the form of a `sinuous feed -to provide a delay line having increased phase differences between signals appearing at successive output junctions therealong. Y In operation, one extremity of the delay line 10 receives a signal having an independently variable frequency from a microwave signal generator 12. In that all transmission line and waveguide have normal dispersion, signals appearing at successive output junctions along .the delay line l0 Ihave a progressively increasing phase delay, the magnitude of which is dependent on the frequency of the signal. If the angular lfrequency appearing at the input of delay line lll is designated as w1, the frequency characteristic of the signal may be represented as cos wlt. Thus, if the phase of the signal appearing at the input of `delay line 4l() is taken as a reference and the ydelay between successive ones of the m output junctions along delay line 1! is c radians for the aforementioned angular frequency w1, the frequency characteristics of the signals appear-ing at the m output Vjunctions of delay line 10 may be represented as follows:

Patented Oct. 24, 1961 Table I Output Junction along I Frequency VDelay t Y n aracteristicnw Zero (ie. Input) cos wlt First cos (olf-rp) Second cos (ult-2e) Y (lL-l) cos [wlf-(n-Dqd n cos [ult-mp] (n+1) COS twlf-(n-tlw] (1n-3) cos [w1t-(m-3) p] (ITL-2) COS [wlt-(m-ZMJII (m-l) cos [wlt-(m-Uqo] m cos [alt-mp] y I'he signal provided by the signal generator 12 and applied to the input of -delay line 1i) fis also applied to a mixer 14 along with a signal of Iangular frequency o2 generated by a microwave signal generator 16. The signals appearing at the output terminals of mixer 14 are appliedl to a filter 18 which operates in a manner to isolate one of the signals having an angular frequency equal to the sum or difference ofthe angular frequencies of the signals generated by the signal generators 12, 16. in the present case, it will be assumed that the lter 18 isolates the signal having an angular frequency equal to the difference in the angular frequency of the signals provided by the generators 12, 16 whereby the frequency characteristic of the signal available at the output of lhis isY i tive mixer 220, 221

3 to any output of the corporate feed 20 the same. Thus, with the electrical length between the input and any output of the corporate feed 2t) being the same, the phasey delay produced by the insertion of the corporate feed 2t) in the path of the signal frequency characterkistic cos (w1-ogy will be the same for a particular vthe corporate feed 29 to the input circuits of one of a series of mixers 220, 221 22m. A filter 24 is then coupled to the output of each of the mixers, 220, 221 22m for the purpose of isolating the signals having an angular frequency equal to the difference between the angular frequencies of the signals applied to the respec- 22m. Thus the frequency characteristic of the signals appearing at the respective outputs ot' the filters 24 corresponding to the mixers 220, 221

. 22m may be represented as follows:

Table II As is evident from Table II, the angular frequency of each output signal appearing at the output of a filter 24 is wz radians per second. It is thus apparent that the frequency,

of the out-put signals is determined by the frequency of the microwave signal generator 16. Further, the phase difference, o, which exists between each successive output signal is determined by the dispersion of the delay line and the frequency of the microwave signal generator i2. In that the dispersion of the delay line 10 remains constant in the present system, the phase difference, qb, may be controlled by selecting the angular frequency, w1. That is, the phase difference, qb, which exists between signals appearing at successive outputs of filters 24 may be controlled by the variable frequency microwave signal generator 12. It is evident that the phase delay, o1, which will change with changes in frequency, will not affect the phase difference between successive output signals of the present apparatus as there will always be cancellation.

What is claimed is:

11. An apparatus for producing a plurality of output signals of the same frequency, successive ones of said signals having a determinable phase diierence, said apparatus comprising a delay line adapted to receive a variable frequency signal at one extremity thereof; means for providing output junctions at a plurality of spaced points along said delay line; a plurality of mixers, each one of said mixers corresponding to a different output junction along said delay line; means for coupling each of said ou-tput junctions to an input circuit of the mixer corresponding thereto; means for applying a signal diifering in frequency from said variable frequency by a predetermined number of cycles per second to the remaining input circuit of each of said plurality of mixers; and means coupled to each of said mixers for isolating the signals appearing at the respective outputs thereof that are of a frequency equal to said `predetermined number of cycles per second.

2. An apparatus for producing a plurality of output signals, successive ones of said signals having variable equal phase dilerences, said apparatus comprising a delay line adapted to receive a variable frequency signal at one extremity thereof; means for providing output junctions at a plurality of uniformly spaced points along said delay line; a plurality of mixers, each one of said mixers corresponding to a different output junction along said delay line and having rst and second input circuits and an output circuit; means for coupling each of said output junctions to the rst input circuit of the mixer corresponding thereto; and means for applying a signal differing in frequency from said variable frequency'by a predetermined number of cycles per second to the second input circuit of each of said plurality of mixers whereby said plurality of output signals are available at the output circuits of said plurality of mixers.

3. The apparatus as defined in claim 2 wherein said delay line constitutes a length of waveguide.

4. The apparatus as defined in claim 2 wherein said delayV line constitutes a length of coaxial line.

5. The apparatus as deiined in claim 2 which includes l additional means for controlling said predetermined num- 30 y plurality of output signals.

ber of cycles thereby to determine the frequency of said 6. An apparatus for producing a plurality of output signals, successive ones of said signals having determinable phase dierences, said apparatus comprising a delay line adapted to receive a variable frequency signal at one extremity thereof; means for providing output junctions at a plurality of spaced points along said delay line; means for providing a source of signals, each of which is of the same phase and of a frequency which differs from said variable frequency by a predetermined number of cycles per second; and a plurality of means for mixing signals, individual ones of said signal mixing means being responsive to the signal available at the output junction corresponding thereto at a spaced point along said delay line and one of the signals provided by said source, thereby to produce said plurality of output signals.

7. An apparatus for producing a plurality of output signals, successive ones of said signals having variable lequal phase differences, said apparatus comprising a rst generator for providing a rst variable frequency microwave signal; a delay line responsive to said iirst variable frequency signal, said delay line having a plurality of output junctions at uniformly spaced points therealong;

a second generator for providing a second variable frequency microwave signals; means responsive to said first and second signals and including a first mixer for `producing a third signal of a frequency equal to the difference in frequency between said first and second signals; a corporate feed responsive to said third signal for providing a plurality of reference signals, each of which vare of the same relative phase and are of a frequency References Cited in the le of this patent UNITED STATES PATENTS 2,680,151 Boothroyd i June 1, 1954 Disclaimer 3,005,960.-Berl D. Levemon, Los Angeles, Calif. AEPARATUS FOR GENERATING MULTIPLE SIGNALS WITH INDEPENDENTLY CONTROLLABLE PHASE DIF- FERENCES AND FREQUENCY. Patent dated Oct. 24, 1961. Disclaimer led Mar. 28, 1962, by the assignee, Hughes Aircraft Oompa/ny.

Herebg enters this disclaimer to claims 2, 3, and 6 of said patent.

[ #Mal Gazette May 8, 1.96

Disclaimer 3,005,960.-Z?el D. Leve/mon, Los Angeles, Calif. APPARATUS FOR GENERA'L'ING MULTELE SIGNALS WITH INDEPENDENTLY CONTROLLABLE PHASE Dm- FERENCES AND FREQUENCY. Patent dated Oct. 24, 1961. Disclaimer liled Mar. 28, 1962, by the assignee, H 14g/zes Aircraft Uompcmy.

Herebg enters this disclaimer to claims 2, 3, and 6 of said patent.

[ yj''al Gazette May 8, 1.962.] 

